The wastewater discharged from commercial kitchens of restaurants and other members of the restaurant industry as well as food plants, processed food plants and other factories contains large amounts of fats and oils, starch, proteins and other contaminants. In particular, the concentrations of fats and oils in wastewater have increased in recent years due to changes in customer needs. Consequently, wastewater treatment is becoming essential at facilities and establishments discharging such wastewater.
Wastewater is typically treated using an activated sludge method. However, activated sludge methods suffer a decrease in treatment capacity of the biological treatment tank as the fat and oil concentration of the wastewater increases. Consequently, wastewater is pretreated using devices such as a pressure flotation device. However, the use of a pressure floatation device requires the use of flocculants and other chemicals and results in the generation of sludge. Therefore, numerous businesses using these devices are burdened with device installation and maintenance costs, chemical costs and sludge treatment costs.
In Japan, all commercial kitchens are required to install grease traps. Grease traps refer to water storage tanks in which the inside of the tank is divided into a plurality of compartments, and are equipped with a water inlet for introducing wastewater and a drain outlet for discharging wastewater to prevent fats and oils present in wastewater from running off directly into the sewer by trapping fats and oils in a trap. Neglecting to clean the grease trap not only results in the generation of a foul odor, but is also unsanitary due to accumulation of fats and oils, sludge and scum. However, the work of cleaning the grease trap is labor-intensive and becomes a burden for many businesses.
In view of these circumstances, attempts have been made to improve the efficiency of wastewater treatment using microorganisms. For example, Patent Document 1 describes a method for degrading oils and reducing levels of n-hexane extracted substances by adding live cultured bacteria and live bacterial preparation of Bacillus subtilis strain BN1001, deposited as Accession No. NITE BP-02608 with NITE Patent Microorganisms Depository of the National Institute of Technology and Evaluation, located at #122 2-5-8 Kazusakamatari, Kisarazu-shi, Chiba 292-0818, Japan, to oil-containing wastewater.